Lighting & Electrical
Given how often a loaded car trailer sits at or near braked-trailer weight thresholds, the electrical setup is less optional than on lighter trailer types.
Required Lighting
- Tail lights, brake lights, indicators — synced to the tow vehicle
- Number plate light
- Reflectors — red rear, amber side
On a car trailer, side marker lights along the full deck length are worth fitting even where not strictly mandatory in every state — the deck is typically longer than a box trailer's body, and clear side visibility matters more for other road users judging the combination's length at night.
Plug Types
7-pin flat or round covers unbraked or mechanically-braked trailers; car trailers fitted with electric or electric-over-hydraulic brakes — common given how often loaded weight pushes into the 2,000kg+ GTM bracket — generally need a 12-pin plug to carry the brake controller circuit in addition to standard lighting.
Brake Controllers
If the trailer has electric brakes, the tow vehicle needs a compatible brake controller wired in — a separate circuit from lighting. Given a loaded car trailer often sits well into the 751kg+ (brakes required) and frequently the 2,000kg+ (all-wheel brakes plus breakaway) brackets covered in the braking systems guide, confirming the tow vehicle's brake controller compatibility before towing matters more here than on lighter trailers.
Questions & Answers
What plug does a car trailer need?
Depends on brake type. Unbraked or mechanically-braked car trailers typically use 7-pin; trailers with electric brakes — common given how heavy a loaded car trailer often is — generally need 12-pin to carry the brake controller circuit.
Do I need a brake controller for a car trailer?
If the trailer has electric or electric-over-hydraulic brakes, yes — the tow vehicle needs a compatible controller wired in. Mechanically-braked (overrun) trailers don't need one at all, since braking is entirely mechanical.